阅读说明：本技术 一种锂电池多孔Fe基非晶态合金包覆硅负极及制备方法 (Porous Fe-based amorphous alloy coated silicon cathode of lithium battery and preparation method ) 是由 陈庆 李国松 于 2019-10-16 设计创作，主要内容包括：本发明属于锂电池负极制备的技术领域,具体涉及一种锂电池多孔Fe基非晶态合金包覆硅负极及制备方法。本发明一种锂电池多孔Fe基非晶态合金包覆硅负极,通过低氧溅射Fe<Sub>48</Sub>Cr<Sub>15</Sub>Mo<Sub>14</Sub>C<Sub>15</Sub>B<Sub>6</Sub>Y<Sub>2</Sub>非晶态合金和氯化钠,再洗涤去除氯化钠,填驻石墨烯,得到一种锂电池多孔Fe基非晶态合金包覆的硅颗粒,这种多孔Fe基非晶态合金的强度高,能有效抑制充放电过程中硅颗粒的体积膨胀,提高负极材料的结构稳定性。Fe基非晶态合金是典型的高强度、低膨胀合金,且耐腐蚀,包覆硅颗粒能减少纳米硅颗粒的团聚,用于锂电池的负极材料,能够有效提高锂电池的循环稳定性能。(The invention belongs to the technical field of preparation of lithium battery cathodes, and particularly relates to a porous Fe-based amorphous alloy coated silicon cathode of a lithium battery and a preparation method thereof. The porous Fe-based amorphous alloy coated silicon cathode of the lithium battery has low through-putOxygen sputtering of Fe 48 Cr 15 Mo 14 C 15 B 6 Y 2 And washing the amorphous alloy and sodium chloride to remove the sodium chloride, and filling graphene to obtain the porous Fe-based amorphous alloy coated silicon particles of the lithium battery, wherein the porous Fe-based amorphous alloy has high strength, can effectively inhibit the volume expansion of the silicon particles in the charging and discharging processes, and improves the structural stability of the negative electrode material. The Fe-based amorphous alloy is a typical high-strength low-expansion alloy, is corrosion-resistant, can reduce the agglomeration of nano silicon particles by coating the silicon particles, is used for a negative electrode material of a lithium battery, and can effectively improve the cycle stability of the lithium battery.)

1. A preparation method of a porous Fe-based amorphous alloy coated silicon negative electrode of a lithium battery is characterized by comprising the following steps:

s1, ball-milling silicon powder serving as a raw material in a ball mill for 5-8 hours to obtain silicon particles with the particle size of 20-80 nm;

s2, compacting sodium chloride in a tabletting machine to prepare sodium chloride tablets with the diameter of 5mm for later use;

s3, passing the silicon particles obtained in the step S1 through a particle accelerator, and entering a low-oxygen double-target sputtering tube at the speed of 10m/S, wherein the Fe with the diameter of 5mm is used as the sputtering tube₄₈Cr₁₅Mo₁₄C₁₅B₆Y₂The amorphous alloy sheet and the sodium chloride pressed sheet are used as target materials, and when silicon particles pass through the low-oxygen sputtering tube, a layer of Fe-based amorphous alloy containing primary pores and sodium chloride mixed film is uniformly sputtered on the surfaces of the silicon particles; after sputtering, removing sodium chloride in the film, and drying to obtain silicon particles coated by the porous Fe-based amorphous alloy film of the lithium battery;

and S4, placing the silicon particles coated by the porous Fe-based amorphous alloy film obtained in the step S3 in a vacuum closed container, adding graphene slurry, uniformly depositing the graphene slurry on the pores and the surface of the porous material, and drying to obtain the porous Fe-based amorphous alloy coated silicon cathode material of the lithium battery.

2. The method for preparing the porous Fe-based amorphous alloy coated silicon negative electrode of the lithium battery as claimed in claim 1, wherein the ball mill in the step S1 is a vacuum atmosphere high-energy ball mill, and the ball milling time is 6 hours.

3. The method as claimed in claim 1, wherein the sodium chloride in step S2 is analytically pure and has a purity of 99.9% or higher.

4. The method for preparing the porous Fe-based amorphous alloy coated silicon negative electrode of the lithium battery as claimed in claim 1, wherein the oxygen content in the atmosphere in the low-oxygen sputtering tube in the step S3 is less than or equal to 3%, and the rest gas is at least one of helium, neon and argon.

5. The method for preparing the porous Fe-based amorphous alloy coated silicon negative electrode of the lithium battery as claimed in claim 1, wherein the voltage in the sputtering tube in the step S3 is 60-80V, the current is 500-600A, and the sputtering distance between the target and the particles is 120 mm.

6. The method for preparing the porous Fe-based amorphous alloy coated silicon negative electrode of the lithium battery as claimed in claim 1, wherein the thickness of the mixed film of the amorphous alloy and the sodium chloride in the step S3 is 3-5 nm.

7. The method as claimed in claim 1, wherein the step S3 of removing the sodium chloride in the film is performed by washing in deionized water to dissolve the sodium chloride in the film.

8. The method for preparing the porous Fe-based amorphous alloy coated silicon negative electrode of the lithium battery as claimed in claim 1, wherein the drying in the step S3 is drying in a drying oven at a constant temperature of 100 ℃ for 2 h.

9. The method as claimed in claim 1, wherein the amount of graphene slurry added in step S4 is 5-15% of the mass of the porous Fe-based amorphous alloy thin film coated silicon particles.

10. The porous Fe-based amorphous alloy coated silicon negative electrode of the lithium battery prepared by the preparation method of any one of claims 1 to 9.

Technical Field

The invention belongs to the technical field of preparation of lithium battery cathodes, and particularly relates to a porous Fe-based amorphous alloy coated silicon cathode of a lithium battery and a preparation method thereof.

Background

With the rapid development of technology, the conventional lithium secondary battery cannot meet the requirement of high specific energy for new energy vehicles, mobile devices, and advanced energy storage devices.

With the improvement of the application development of electric vehicles on the battery demand, the energy density of the lithium ion battery is continuously improved, compared with the traditional graphite cathode, the silicon has ultrahigh theoretical specific capacity (4200 mAh/g) and lower lithium removal potential, the voltage platform of the silicon is slightly higher than that of the graphite, lithium is difficult to precipitate on the surface during charging, and the safety performance is better. Silicon becomes one of the potential choices for upgrading and updating carbon-based cathodes of lithium ion batteries, and becomes an ideal cathode material.

However, silicon has disadvantages as a negative electrode material for lithium ion batteries. Silicon is a semiconductor material and has low intrinsic conductivity. In the electrochemical cycle process, the insertion and extraction of lithium ions can cause the volume of the material to expand and contract by more than 300%, the generated mechanical acting force can gradually pulverize the material, the structure is collapsed, and finally, the electrode active substance is separated from the current collector, the electric contact is lost, and the cycle performance of the battery is greatly reduced. In addition, silicon has difficulty in forming a stable Solid Electrolyte Interface (SEI) film in an electrolyte solution due to such a volume effect. With the destruction of the electrode structure, new SEI films are continuously formed on the exposed silicon surface, which aggravates silicon corrosion and capacity fade.

In order to improve the cycle performance of the silicon-based negative electrode and improve the structural stability of the material in the cycle process, the silicon material is generally subjected to nano-crystallization and composite treatment. Currently, the main research directions for the nano-crystallization of silicon materials include: silicon nanoparticles (zero-dimensional nanocrystallization), silicon nanowires/tubes (one-dimensional nanocrystallization), silicon thin films (two-dimensional nanocrystallization), 3D porous silicon, hollow porous silicon (three-dimensional nanocrystallization); the main research directions for the silicon material compounding include: silicon/metal type composites, silicon/carbon type composites, and ternary type composites (e.g., silicon/amorphous carbon/graphite ternary composite systems).

During the charge and discharge cycle of the silicon negative electrode material, the silicon negative electrode has obvious volume change to cause the electrode material to be broken and form an unstable electrode-electrolyte interface, so the cycle life of the electrode is limited. The silicon nano particles and the three-dimensional porous silicon can inhibit the volume effect of the material to a certain extent, and simultaneously can reduce the diffusion distance of lithium ions and improve the electrochemical reaction rate. However, they have large specific surface areas, which increase direct contact with the electrolyte, resulting in side reactions and an increase in irreversible capacity, and a decrease in coulombic efficiency. In addition, the silicon active particles are easy to agglomerate in the charging and discharging process, and electrochemical sintering is generated, so that capacity fading is accelerated.

The silicon nanowire/tube can reduce the radial volume change in the charging and discharging process, realize good circulation stability and provide a rapid lithium ion transmission channel in the axial direction. But the tap density of the silicon material is reduced, so that the specific volume capacity of the silicon negative electrode is reduced. The silicon film can reduce the volume change generated in the direction vertical to the film and maintain the structural integrity of the electrode. However, after many cycles, the silicon thin film is easily broken and separated from the substrate, and the preparation cost of the silicon thin film is high.

Chinese patent application No. 200610068076.3 discloses a negative electrode for a lithium ion secondary battery, a method for preparing the same, and a lithium ion secondary battery using the same, providing a negative electrode for a lithium ion battery having high capacity, excellent cycle performance, and discharge performance under high load. In an anode for a lithium ion secondary battery comprising a current collector and an active material layer supported on the current collector, the active material layer comprising silicon and an element M that is not capable of forming an alloy with lithium; the proportion of the element M in a first face in contact with the current collector is higher than that in a second face opposite to the first face in the thickness direction of the active material layer; element M is different from the element forming the current collector; and the active material layer does not include a binder.

Chinese patent application No. 201510545414.7 discloses a graphene-doped hollow porous carbon/silicon nanofiber lithium battery negative electrode material and a preparation method thereof, and the graphene-doped hollow porous carbon/silicon nanofiber lithium battery negative electrode material is formed by uniformly dispersing silicon nanoparticles and graphene in a carbon nanofiber matrix. The preparation method comprises the following steps: the preparation method comprises the steps of taking a mixed solution of polyacrylonitrile/polymethyl methacrylate/ethyl orthosilicate/graphene oxide as a shell solution, taking a polymethyl methacrylate solution as a core solution, obtaining polyacrylonitrile/polymethyl methacrylate/silicon dioxide nano fibers doped with graphene oxide by using a coaxial electrostatic spinning technology, pre-oxidizing the obtained nano fibers at the temperature of 200-plus-300 ℃, then carrying out high-temperature carbonization at the temperature of 500-plus-1000 ℃, and finally carrying out thermal reduction by using magnesium powder to obtain the graphene-doped hollow porous carbon/silicon nano fiber lithium battery cathode material.

Chinese invention patent application No. 201811542597.7 discloses a low-cost preparation method of a stable lithium battery silicon negative electrode, which comprises uniformly mixing silicon-based nanoparticles, liquid silicon rubber and ethylene-vinyl acetate copolymer in a mass ratio of 10:3:1, heating to melt and disperse, and uniformly dispersing the silicon-based nanoparticles in a melt; adding a curing agent, graphene powder and carbon fibers into the melt prefabricated in the step (1), and performing ultrasonic dispersion to obtain a slurry; and coating the slurry on the surface of a negative current collector, curing for 2 hours at the temperature of 80 ℃, drying, slitting and tabletting to obtain the silicon negative electrode of the lithium battery.

Disclosure of Invention

The method aims at the defects of poor structural stability, poor cycle performance, easy agglomeration of nano-silicon particles and the like of the lithium battery caused by large volume change of the conventional silicon cathode. The invention provides a porous Fe-based amorphous alloy coated silicon negative electrode of a lithium battery and a preparation method thereof.

The invention relates to a preparation method of a porous Fe-based amorphous alloy coated silicon negative electrode of a lithium battery, which comprises the following steps:

s1, ball-milling silicon powder serving as a raw material in a ball mill for 5-8 hours to obtain silicon particles with the particle size of 20-80 nm;

s2, compacting sodium chloride in a tabletting machine to prepare sodium chloride tablets with the diameter of 5mm for later use;

s3, passing the silicon particles obtained in the step S1 through a particle accelerator, and entering a low-oxygen double-target sputtering tube at the speed of 10m/S, wherein the Fe with the diameter of 5mm is used as the sputtering tube₄₈Cr₁₅Mo₁₄C₁₅B₆Y₂The amorphous alloy sheet and the sodium chloride pressed sheet are used as target materials, and when silicon particles pass through the low-oxygen sputtering pipe, the silicon particlesA layer of Fe-based amorphous alloy containing primary pores and a sodium chloride mixed film are uniformly sputtered on the surface; after sputtering, removing sodium chloride in the film, and drying to obtain silicon particles coated by the porous Fe-based amorphous alloy film of the lithium battery;

and S4, placing the silicon particles coated by the porous Fe-based amorphous alloy film obtained in the step S3 in a vacuum closed container, adding graphene slurry, uniformly depositing the graphene slurry on the pores and the surface of the porous material, and drying to obtain the porous Fe-based amorphous alloy coated silicon cathode material of the lithium battery.

The vacuum atmosphere high-energy ball mill comprises models of GN-2, GN-3 and the like, is used for rapidly crushing various materials (including solid particles, magnetic materials and the like) to achieve ultrafine particles, and can be small-sized mechanical equipment for alloying different metals and non-metals (including high-temperature non-melting metals), particularly in the field of surface nanocrystallization. Further, in the preparation method of the porous Fe-based amorphous alloy coated silicon negative electrode for the lithium battery, the ball mill in the step S1 is a vacuum atmosphere high-energy ball mill, and the ball milling time is 6 hours.

Further, in the preparation method of the porous Fe-based amorphous alloy coated silicon negative electrode for the lithium battery, in step S2, the sodium chloride is analytically pure, and the purity is greater than or equal to 99.9%.

The sputtering target refers to a sputtering source which forms various functional films on a substrate through sputtering deposition under proper process conditions by magnetron sputtering, multi-arc ion plating or other types of coating equipment. Further, in the preparation method of the porous Fe-based amorphous alloy coated silicon negative electrode for the lithium battery, in step S3, the oxygen content in the atmosphere in the low-oxygen twin-target sputtering tube is not more than 3%, and the rest gas is at least one of helium, neon and argon.

Further, in the preparation method of the porous Fe-based amorphous alloy coated silicon cathode for the lithium battery, in the step S3, the voltage in the sputtering tube is 60-80V, the current is 500-600A, and the sputtering distance between the target and the particles is 120 mm.

Further, in the preparation method of the porous Fe-based amorphous alloy coated silicon negative electrode of the lithium battery, the thickness of the mixed film of the amorphous alloy and sodium chloride in the step S3 is 3-5 nm.

Further, in the above method for preparing the porous Fe-based amorphous alloy coated silicon negative electrode for a lithium battery, the step S3 is to wash the film to remove sodium chloride in deionized water, and dissolve the film to remove sodium chloride.

Further, in the preparation method of the porous Fe-based amorphous alloy coated silicon negative electrode for the lithium battery, the drying in the step S3 is drying for 2 hours at a constant temperature of 100 ℃.

Further, in the preparation method of the porous Fe-based amorphous alloy coated silicon negative electrode of the lithium battery, the addition amount of the graphene slurry in the step S4 is 5-15% of the mass of the porous Fe-based amorphous alloy film coated silicon particles.

The invention also provides a porous Fe-based amorphous alloy coated silicon negative electrode of the lithium battery prepared by the preparation method.

The invention relates to a preparation method of a porous Fe-based amorphous alloy coated silicon cathode of a lithium battery, which is characterized in that Fe is sputtered under low oxygen₄₈Cr₁₅Mo₁₄C₁₅B₆Y₂And washing the amorphous alloy and sodium chloride to remove the sodium chloride, and filling graphene to obtain the porous Fe-based amorphous alloy coated silicon particles of the lithium battery, wherein the porous Fe-based amorphous alloy has high strength, can effectively inhibit the volume expansion of the silicon particles in the charging and discharging processes, and improves the structural stability of the negative electrode material. The Fe-based amorphous alloy is a typical high-strength low-expansion alloy, is corrosion-resistant, can reduce the agglomeration of nano silicon particles by coating the silicon particles, is used for a negative electrode material of a lithium battery, and can effectively improve the cycle stability of the lithium battery.

Detailed Description

The present invention will be described in further detail with reference to specific embodiments, but it should not be construed that the scope of the present invention is limited to the following examples. Various substitutions and alterations can be made by those skilled in the art and by conventional means without departing from the spirit of the method of the invention described above.